The present invention relates to the general field of aeronautics.
It concerns more particularly the monitoring of an aircraft engine, equipped with a sensor designed to hold back metallic particles taken in by the lubricating oil of the engine resulting from wearing of moving pieces.
As is known, the moving pieces of an aircraft engine, such as gears or bearings, are subjected to wearing phenomena such as scaling. These wearing phenomena are evident especially in the appearance of particles of a more or less large size in the lubrication circuit of the engine. These particles play a major role in detecting and providing engine breakdown.
In fact, as shown in the graph of FIG. 1, the production of particles Ppart in an engine comprising moving pieces evolves over time t. More precisely, during a phase 1 of running-in, the production rate of particles is relatively high and decreases progressively. The running-in phase 1 is followed by a normal use phase 2, during which production of particles stabilises. Finally, during a terminal wear phase 3, wear on more loaded pieces involving a higher particle production rate, including bursting if no maintenance is done.
The use of sensors (or detectors) of particles in the lubrication system of the engine therefore monitors the presence of these particles, and even the status of the engine. Preventive maintenance on the engine is then feasible, especially when large-size particles are detected in an abnormal quantity, which might anticipate an engine breakdown.
An example of such a sensor is an electromagnetic plug, also known by the name “Electric Chip Detector” (ECD) or “Electro Magnetic Chip Detector” (EMCD) in English, located in the lubrication system of the engine upstream of the filters. Such a plug advantageously detects, simply and automatically, without need for visual monitoring, the metallic particles carried along in the engine oil. The invention preferably applies to this type of sensor.
As is known, an electromagnetic plug is equipped with a magnet surrounded by two conductive electrodes insulated from each other, and separated by a gap integrated in an electric circuit. When a large quantity of metallic particles circulates in the lubrication system, the latter are captured by the magnet and shunt (i.e. short-circuit) the gap of the electromagnetic plug, making contact between the two electrodes. The resulting contact causes a drop in resistance measured between the electrodes.
A processing circuit linked to the plug and integrated for example in the engine controller (or FADEC, Full Authority Digital Engine Control), compares the measured resistance between the electrodes of the plug to a threshold value and when this threshold value is exceeded generates a warning message for an engine maintenance system or for the pilot of the aircraft. When this message is received, the plug can then be disassembled for more advanced analysis of the state of the particles or for maintenance work.
Such functioning advantageously avoids periodic control of the particle sensor, and especially disassembly of the latter in the absence of a warning message. However, the threshold value of the resistance from which a warning message is generated is difficult to determine, the latter depending on several parameters including especially engine type, application, engine age, environmental context, etc.
In this way, for safety reasons, there is a tendency to consider a sufficiently high threshold value so as not to neglect a critical engine wear situation. However, the flip side to using a high threshold value is a high rate of false alarms, limiting the impact of such a plug.
There is therefore a need for process and a monitoring device which does not have these disadvantages and uses electromagnetic plugs currently deployed on numerous aircraft.